Article having corrosion resistant coating

Abstract

According to the invention, an article that is exposed to high temperatures, e.g., over 1000° C. during operation is disclosed. In one embodiment, a turbine blade for a gas turbine engine includes a directionally solidified metallic substrate, e.g., a superalloy, which defines an airfoil, a root and a platform located between the blade and root. The platform has an underside adjacent the root, and a corrosion resistant noble metal-containing aluminide coating is located on portions of the blade susceptible to corrosion and/or stress corrosion cracking, such as the underside of the platform and the neck. The applied coating prevents corrosion and stress corrosion cracking of blade in these regions.

What is claimed is:  
     
       1. A superalloy gas turbine component which operates in an environment with primary gas path temperatures in excess of 1000° C., the component having a first, exposed portion which is directly exposed to hot gas path, a second, shielded section which is shielded from direct exposure to the hot gas path, and a third section between the exposed and shielded portions, the improvement which comprises a corrosion resistant platinum aluminide coating applied to the third section. 
     
     
       2. The component of  claim 1  comprising a turbine blade, the first portion forming an airfoil, the section portion forming a root, and the third section forming a platform, the improvement comprising a corrosion resistant platinum aluminide coating applied to the underside of the platform. 
     
     
       3. The component of  claim 1 , wherein the components is composed of a directionally solidified superalloy material. 
     
     
       4. The component of  claim 1 , wherein the coating has a nominal thickness of less than about 0.005″. 
     
     
       5. The component of  claim 1 , wherein the coating further comprises varying levels of hafnium, silicon and yttrium or mixtures thereof. 
     
     
       6. The turbine blade of  claim 1 , wherein at least a portion of the component has an applied coating having a composition different from that applied to the airfoil surface. 
     
     
       7. The turbine blade of  claim 1 , wherein at least a portion of the airfoil is coated by a diffusion aluminide and the underplatform is coated with a noble metal-containing aluminide. 
     
     
       8. The turbine blade of  claim 1 , wherein the coating further comprises yttrium, hafnium and silicon mixtures thereof.